黄土水敏性及其时空分布规律
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摘要
黄土是一种具有水敏性的特殊土,天然状态下可以长期保持直立高陡的状态,遇水后呈现出崩解、湿陷、滑动、流变等变形行为。开展黄土的水敏性特性及其时空分布规律研究,对指导黄土高原工程建设和防灾减灾具有重要的现实意义。笔者在非饱和土力学的框架下,引入吸应力的概念,对黄土的水敏性及其力学机制进行解释,即水敏性的本质是,随着含水率的增大,土体内部吸应力逐渐减小,对应不同的外界边界条件时,产生崩解、湿陷、滑动、流变等不同的宏观变形行为。在黄土高原从西到东、从北向南不同空间位置的黄土剖面的不同的层位,系统采集黄土样品,基于TRIM试验测试技术,开展样品的土-水特征曲线与吸应力特征曲线测试。试验结果表明,脱湿与吸湿条件下的各曲线呈现相同的变化规律,均存在3个明显的特征段。黄土对水的敏感程度随其沉积年代和在黄土高原分布位置的不同,呈现出规律性的变化。空间上,从西向东、由北向南,水敏性增强;时间上,沉积年代由老到新,水敏性增强。
Loess is a kind of special soil with high water sensitivity,and the loess with natural water content can keep high and steep stable for a long time.However,when water comes,it shows strong water sensitivity of disintegration,dissolution,liquefaction,creep,and sliding.Research on the water sensitivity of loess and its special-temporal distribution has a practical significance to guide the engineering constructions in the unsaturated loess area.Based on the theory of unsaturated loess,the concept of suction stress is introduced to explain the water sensitivity of loess.The essence of water sensitivity is,the suction stress decreases with the increase of water content,and the different deformation behaviors will occur under different boundary conditions.Loess samples have been collected along sections from west to east and north to south of the Loess Plateau for obtaining their curves of SWCC and SSCC with TRIM technique.The results show that,these curves change similarly and show three distinct sections under both drying and wetting conditions.The water sensitivity of loess varies regularly with sedimentary dates and locations in the Loess Plateau.From west to east,north to south,the water sensitivity of loess is increasing;In terms of time,the water sensitivity of loess is increasing from old to new sedimentary age.
Loess is a kind of special soil with high water sensitivity,and the loess with natural water content can keep high and steep stable for a long time.However,when water comes,it shows strong water sensitivity of disintegration,dissolution,liquefaction,creep,and sliding.Research on the water sensitivity of loess and its special-temporal distribution has a practical significance to guide the engineering constructions in the unsaturated loess area.Based on the theory of unsaturated loess,the concept of suction stress is introduced to explain the water sensitivity of loess.The essence of water sensitivity is,the suction stress decreases with the increase of water content,and the different deformation behaviors will occur under different boundary conditions.Loess samples have been collected along sections from west to east and north to south of the Loess Plateau for obtaining their curves of SWCC and SSCC with TRIM technique.The results show that,these curves change similarly and show three distinct sections under both drying and wetting conditions.The water sensitivity of loess varies regularly with sedimentary dates and locations in the Loess Plateau.From west to east,north to south,the water sensitivity of loess is increasing;In terms of time,the water sensitivity of loess is increasing from old to new sedimentary age.
引文
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高国瑞.黄土显微结构分类与湿陷性[J].中国科学,1980,(12):1203-1208.GAO Guorui.Classification of micro pores and collapsibility[J].Science in China,Ser.A,1980,(12):1203-1208(in Chinese).
许领,戴福初,金艳丽.从非饱和土力学角度探讨黄土湿陷机制[J].水文地质工程地质,2009,(4):62-65.XU Ling,DAI Fuchu,JIN Yanli.Discussion on the mechanism of loess collapsibility from the perspective of unsaturated soil mechanics theory[J].Hydrogeology&Engineering Geology,2009,(4):62-65(in Chinese).
刘东生,黄土与环境[M].北京:科学出版社,1985.LIU Dong sheng.Loess and environment[M].Beijing:China Science Publishing&Media Ltd,1985(in Chinese).
张宗祜.中国黄土[M].北京:地质出版社,1989.ZHANG Zonghu.Loess in China[M].Beijing:Geological Publishing House,1989(in Chinese).
王永炎,林在贯.中国黄土的结构特征及物理力学性质[M].北京:科学出版社,1990.WANG Yongyan,LIN Zaiguan.Structure characteristics,physical and mechanical properties for loess in China[M].Beijign:China Science Publishing&Media Ltd,1990(in Chinese).
HOUSTON,S.L.,HOUSTON,W.N.and Wagner,A.Laboratory filter paper suction measurements[J].Geotechnical Testing Journal,1994,17(2):185-194.
LU N.,LIKOS W.J.Suction stress characteristic curve for unsaturated soil[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,48(9):131-142.
徐张建,林再贯,张茂省.中国黄土与黄土滑坡[J].岩石力学与工程学报,2007,26(7):1297-1312.XU Zhangjian,LIN Zaiguan,ZHANG Maosheng.Loess in China and loess landslides[J].Chinese Journal of Rock Mechanics and Engineering,2007,26(7):1297-1312(in Chinese).
张茂省,胡炜,孙萍萍,等.黄土水敏性与水致黄土滑坡研究现状与展望[J].地球环境学报,2016,7(4):323-334.ZHANG Maosheng,HU Wei,SUN Pingping,et al.Advances and prospects of water sensitivity of loess and the induced loess landslides[J].Journal of Earth Environment,2016,7(4):323-334(in Chinese).
谢定义.试论中国黄土力学研究中的若干新趋向[J].岩土工程学报,1999,19(4):273-284.XIE Dingyi.The past,present and future of the research on mechanical characteristics and application of loess[J].Underground Space,1999,19(4):273-284(in Chinese).
张珊珊,张茂省,孙萍萍,等.面向黄土地质灾害的优势流研究[J].兰州大学学报:自然科学版,2019,55(2):274-280.ZHANG Shanshan,ZHANG Maosheng,SUN Ping ping,et al.advances and outlooks of preferential flow study in unsaturated soils[J].Journal of Lanzhou University:Natural Sciences,2019,55(2):274-280.
冯立,张茂省,孙萍萍,等.非饱和土脱湿与吸湿水力特性对比研究[J].水文地质工程地质,2016,43(2):134-139.FENG Li,ZHANG Maosheng,SUN Pingping,et al.Astudy of the hydro-mechanical properties of unsaturated loess under the dying and wetting path[J].Hydrogeology&Engineering Geology,2016,43(2):134-139(in Chinese).
孙建中.黄土学(上篇)[M].香港:香港考古学会出版,2005.SUN Jianzhong.Loessology(Vol.1)[M].Hongkong:Hongkong archaeological society,2005(in Chinese).
雷祥义.中国黄土的孔隙类型与湿陷性[J].中国科学(B辑),1987,(12):1309-1316.LEI Xiangyi.Types of micro pores and collapsibility of loess in China[J].Science in China,Ser.B,1987,(12):1309-1316(in Chinese).
高国瑞.黄土显微结构分类与湿陷性[J].中国科学,1980,(12):1203-1208.GAO Guorui.Classification of micro pores and collapsibility[J].Science in China,Ser.A,1980,(12):1203-1208(in Chinese).
许领,戴福初,金艳丽.从非饱和土力学角度探讨黄土湿陷机制[J].水文地质工程地质,2009,(4):62-65.XU Ling,DAI Fuchu,JIN Yanli.Discussion on the mechanism of loess collapsibility from the perspective of unsaturated soil mechanics theory[J].Hydrogeology&Engineering Geology,2009,(4):62-65(in Chinese).
刘东生,黄土与环境[M].北京:科学出版社,1985.LIU Dong sheng.Loess and environment[M].Beijing:China Science Publishing&Media Ltd,1985(in Chinese).
张宗祜.中国黄土[M].北京:地质出版社,1989.ZHANG Zonghu.Loess in China[M].Beijing:Geological Publishing House,1989(in Chinese).
王永炎,林在贯.中国黄土的结构特征及物理力学性质[M].北京:科学出版社,1990.WANG Yongyan,LIN Zaiguan.Structure characteristics,physical and mechanical properties for loess in China[M].Beijign:China Science Publishing&Media Ltd,1990(in Chinese).
HOUSTON,S.L.,HOUSTON,W.N.and Wagner,A.Laboratory filter paper suction measurements[J].Geotechnical Testing Journal,1994,17(2):185-194.
LU N.,LIKOS W.J.Suction stress characteristic curve for unsaturated soil[J].Journal of Geotechnical and Geoenvironmental Engineering,2006,48(9):131-142.